This invention relates to recessed handgrip features for liquid under pressure e.g. carbonated beverage containers, including bottles, made of a plastics and to methods and apparatus for producing such containers.
xe2x80x9cPlasticsxe2x80x9d are polymerizable materials that can be bi-axially oriented, e.g. polyethylene terephthalate (PET), polypropylene (PP) and acrylonitrile (AN) for use in containers for liquid under pressure, e.g. carbonated beverages.
xe2x80x9cPETxe2x80x9d as used herein shall be construed as including all materials defined hereinbefore as xe2x80x9cPlasticsxe2x80x9d.
xe2x80x9cHandgripxe2x80x9d as used herein is a circular feature formed by a deformation of the wall, which includes a shoulder, of a plastics container which does not extend outwardly (relative to the axis of the container) from the outer surface of the container even when the container contains liquid under pressure, e.g. a carbonated beverage, and is exposed to industry defined test procedures for such containers including exposure to stresses resulting from pressure and elevated temperatures during filling, packaging, distribution, sale and the end user actions.
xe2x80x9cCircularxe2x80x9d as used herein with respect to handgrips shall be construed to include ovals, ellipses, teardrops, circular segments and other rounded shapes as well as circular shapes
xe2x80x9cContainerxe2x80x9d as used herein shall be construed to include plastics bottles.
xe2x80x9cFrustumxe2x80x9d as used herein shall be construed as a truncated hollow right circular cone in which the apex is replaced by a plane section parallel to the cone base and which has parallel inner and outer surfaces and shall be construed to include a hollow cylinder which has parallel inner and outer surfaces.
In the past, different designs have been used to make a bottle meet specifications. The typical failure for a bottle is in the grip area or deep contour which will expand (creep) upon pressurization (carbonation) and/or higher than room temperatures. Typical bottle tests call for PET bottles to be pressurized to 4.0 volumes of CO2 (xcx9c55 psi at room temperature) and then placed in an oven for 24 hours at 100xc2x0 F. At this temperature, the gas pressure rises to xcx9c95 psi. In addition to the higher forces applied to the plastic walls, the elastic modulus of the plastic is also slightly lower due to the higher temperature. Due to geometry, the bottles will creep in such a way distorting to the point of eliminating any grip or contour design elements in the sidewall of the bottle.
Some geometric designs will resist the creep and try to retain their original shape, but generally a good percentage of the shape is lost. U.S. Pat. No. 5,803,290 shows one design that claims to hold a significant portion of the shape.
PET for carbonated beverage containers has been used for many years. Many different shapes have been suggested to provide handgrips to easy user handling of these containers.
An object of the present invention is to provide a plastics container for liquids under pressure, e.g carbonated liquid beverages having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall.
A further object of the present invention is to provide a blow mold design for producing a blow molded plastics container having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall.
Another object of the present invention to provide a method of producing a plastics container having stable handgrip features, in a wall thereof, which do not extend outwardly from that wall.
According to the invention there is provided a handgrip formed in a wall of a plastics container, the wall defining an interior of the container, an interior surface, an exterior surface and a wall thickness and being suitable for containing a carbonated beverage, comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall.
Additionally frustums may be provided to interconnect domes, rings and troughs not otherwise so provided.
The troughs preferably increase in diameter from the dome to the wall of the container and the troughs and frustums increasingly extend further into the container relative to the wall, from the outermost trough and frustum to the dome.
Also according to the invention there is provided a plastics container for liquids under pressure having at least one handgrip, formed in a wall of the plastics container, the wall defining an interior of the container, an interior surface, an exterior surface and a wall thickness, the handgrip comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall.
In addition, according to the invention there is provided a blow mold for blow molding a plastics container for liquids under pressure having at least one handgrip formed in a wall defining an interior of the plastics container and having, an interior surface, exterior surface and a wall thickness, the handgrip comprising an integral structure formed of a central dome having a convex surface facing an adjacent portion of the exterior surface, at least two concentric rings each having an annular concave surface facing the interior, at least two annular troughs, disposed between the concentric rings, each having an annular concave surface facing an adjacent portion of the exterior surface; a frustum interconnecting one of the dome to the innermost trough and the innermost trough to the innermost ring; and further frustum(s) each interconnecting one of the rings to the next outer trough and next outer trough to the next outer ring, the outermost ring joining integrally the container wall surrounding the handgrip, the handgrip having a thickness approximately equal to the wall thickness wherein the handgrip does not extend radially outwardly from the wall.
The invention also provides a method of producing a handgrip, in a plastics container for pressurized liquids, which does not, in use, extend outwardly from the outer surface of the container, comprises:
a) providing a blow mold having an axis and handgrip forming features in the form of at least two concentric annular projections, to form a handgrip, extending toward the axis of the mold cavity and container to be formed, each annular projection having an outer extremity and adjacent side surface complimentary to a trough and a frustum;
b) pre-heating a preform to facilitate blow molding to form the container and the handgrip;
c) introducing the preform into the blow mold;
d) applying a gas at a pressure sufficient to inflate and deform the preform into contact with the mold cavity to form the container and into contact with handgrip forming features to produce the handgrip in a wall of the container, the handgrip being formed failing to contact the mold cavity in the region of a central dome and a substantial portion of trough connecting rings of the handgrip;
e) cooling the container; and
f) removing the container with the handgrip(s) formed therein from the blow mold cavity.